Production of azo dyestuff images from n-acyl-n-aryl hydrazine developers



"I'WMLJ Patented Jan. 17, 1950 PROBUGTIONnOR-AZO DYESTUFF IMAGES FROM; :Ne-AGYLsNJeARYL Hypnezrnn f 132:;

vspoPERs William E. Hanford, Easton lat, assignor to Gen;

ements. & X33299??? .Fijrn Corporation, New- York} 1 o n ofDelaware- Application Febrnaryggl,351%,;

Serial No. 579,681

(Clr95-v38):

Noprawing.

13 Claims. presen intenti n. -WFQPEP QQi 11 t te i ww color-forming components.

One of the methods widely proposed for use at the present met ts ne mqqep nl 1,9 19?!r graphic color wimages involves the so ecalled c'olorforming development method. By this procedure, quinoneimine and azo methine dyestuffs are produced in situwith a silver image by reacting a, color-forming component such as a phenol or a compound having a reactive methylene group with the oxidation products of a primary arometiee si aeey leizetv. f the s hi h; t

These inethods may be generally cla-ssified into two-groups, (be in wh-ich the az o idyes-are employed to pre-dye the photographic emulsions} the dyes being subsequently destroyed at the places defined by the silver image, and. (2) in which the azo dyestuff images are produced from colorless. components during. -the l processingflof thenfilmtl M I 7* The firstof these two-methods is known as the silver efbleae iineimsth ei ed em of application is illustrated in, forifistan cefU. S. P. 2,020,775. Many ran ifications ofl the second method have been proppsed i rl the prior art. One of these (see U. S. P51358572) involves the incorporation in the emulsion of insolubilized. azo 922 .95 q mzseeemeeeels i zet e l m xe After exposure and development; th xfiiilsion is subjected to the actiono fe bleaching bath which hardens tfie en iulsion attire places defined by the silver images; Upon subsequently treating th he bath opemulsion diazotization bat fl t are capabl pf form wettest. of t i lietitfi tl w.

i g silver antidiapotateslAcdiiiicuit erates onl y where the film" has been unhardened:

components present in theLeinuisi n.

Another, method (see U-Q- diazon ium compounds cording" to this gpr cediji re; a silver image is eac ed mist ea d: t ae ke ienti eee et to caiis e l reac ti on be ween the bI eached silver imageian d the anti iazotatje to form theisiiveri antidiazotate. The wetr soli bleialliali -ant i-- ee ete i inen .rem ye tpv. v st -1 9 2 J in iesfireetsdse eu eieh t e t nfi 0 s i xv 1. 7 92.7 .l eer ee. flees? az9 2etev ees l herew thF M IQ: 139 a dyestllfli e fi:

sun an ther method (see U. s. 1= 2, 3 1 ,2, eg5 nyp s mer mpf i v ma esgmtv soluble s v t masewhi aare in 1 43 3 9? iq en ,u edjtqli rb n e zmq-eiaz'pnmm e b lte 1,1 h u te t e iedect qnp 9, y i t s nfi unl'p t ith n e m nlente A further method (-se'U. s. P, 2,333,12fiilprq- P9555 to nee m ein. n l mu sip n u l n verted i to in oluble zinc salt images, The latter sion an dt o then couple the coupling component ihesel um.. .m qlmd t e Presen not a bee. y metal salt. Through t e age noy .of 1 .1 22,

he ymetaL-salt,thedyestuffi is formedfin the ts' s reetr mu h ly ima e-i pf-t fi Proc s-cw e iy 3 5 hat/Fe er: tain shortcomings, which have mi litated against the adoption thereof ,by the art, ior prac tical putposes, The ,silver dye bleaching method. for in:

eefe t ifiv fr dea I x clt e esqdm nz ee aybe-1 g 0 e1ement's th'rough1 theilsualialzotdy coupling heses? dy ime s Ihasm v ha th b bn 1 r e rl s wheeief pr re A theu q ey do. nt t s g lte 'sr si e its b ea hwettest n ine 2- he at;

e est-Sly eesaui te edi P -a e the process partakes of the simplification of the color-forming development method but gives in lieu of the azo methine and quinoneimine dyes, the more durable azo dyes. With this process, colored photographic negatives, positives or prints comprising one or more layers can be obtained with a high degree of accuracy without encountering the problems inherent in the use of the known methods.

It is accordingly an object of the present invention to produce azo dyestufi images while using N-acyl-N-aryl hydrazines as color developers.

It is a further object of the present invention to produce azo dye images by subjecting an exposed emulsion to the action of a color developer comprising an N-acyl-N-aryl hydrazine and a coupling component.

It is a further object of this invention to produce azo dyestuff images from an emulsion containing a non-diffusing azo coupling component by subjecting the emulsion after exposure to development in an alkaline developer containing an N-acyl-N-aryl hydrazine.

It is a further object of the present invention to produce azo dyestufi positive images by the reversal method while using N-acyl-N-aryl hydrazines as the color developer.

It is a further object of this invention to produce azo dyestuif images by using an N-acyl-N- aryl hydrazine as both a color developer and as a coupling component.

It is a further object of this invention to produce azo dyestufi images in an emulsion containing as the color components an N-acyl-N-aryl hydrazine and a non-diffusing azo coupling component and developing the film by means of an alkaline solution.

x A further object of this invention is a photographic emulsion containing an N-acyl-N-aryl hydrazine as a color-forming component.

A further object of this invention is a photographic emulsion containing a coupling component and an N-acyl-N-aryl hydrazine as a developing component.

Other and further important objects of this invention will be apparent as the description proceeds.

The basis on which the present invention is predicated is the discovery that when N-acyl-N- aryl hydrazines are subjected in an alkaline medium to the action of an oxidizing agent in the presence of a coupling agent usual in the formation of azo dyes, an azo dyestufi is produced. Thus it was discovered that when adding a small amount of 2-phenyl semicarbazide to a sodium carbonate solution of R-salt and incorporating in the solution a small amount of an oxidizing agent such as a few crystals of potassium periodate, a red dye is formed immediately on the surface of the crystals of the oxidizing agent. Acting on this discovery, attempts were made to ascertain if an exposed silver halide could be substituted for the oxidizing agent and condition the N-acyl-N-aryl hydrazine for coupling with the coupling com ponent. It was found that the phenomenon previously mentioned was realized when treating an exposed silver halide with an N-acyl-N-aryl hydrazine in the presence of a coupling component. The N-acyl-N-aryl hydrazine operates to convert the exposed silver halide to silver and is simultaneously conditioned for coupling with the coupling component. It was further ascertained that this result was. achieved irrespective of the nature of the latent silver image involved, that is, whether it was an original latent image, a

( (ITT-N[Y]I) Ac z and these may be used as such or in the form of r their salts, which have the following constitution:

(Ar) N-N[Y]i.H+x-) In these formulae, Ar is a monoor polyvalent radical derived from a compound having an aromatic character, such as benzene, napthalene,

anthracene, phenanthrene, pyrazole, thiazole,

pyrrole, furane, thiophene or the like, Ac is an acyl group or a group of similar character such as in which R. is hydrogen, alkyl such as ethyl, methyl, propyLrbutyl, amyl, octyl, decyl, stearyl and the like, aralkyl such as benzyl and the like, or a radical of aromatic character such as phenyl, toluyl, methoxy phenyl, naphthyl, diphenyl, anthryl, phenanthryl, pyrazolyl and the like, M is a metallic cation or a cation of an inor ganic base, i. e., ammonium and the like or an organic base such as pyridinium, morpholinium and the like, Z is an integer from 1 to 3, and Y is hydrogen or a group which is readily removed by a modification of the pH of the solution such as tion involved:

(Ar) (N-NH:

Examples of the N-acyl-N-aryl hydrazines which fall within the above category and which I have found to be effective for my purpose are:

2-phenyl semicarbazide of the formula Bis-2.2"(4.4'-diphenylene)-semlcarbazide of the formula.

HgN-IEWIi-NH,

" NH: Y N11,

-' 4-B-maphthy1-2-phnyl 'semicarbazide of the formula N-hehzoyl-N-(S-chlorophenyl)hydrazine: sulfate of the formula I N-phenyl-N-stearoyl hydrazine sulfate of the formula.

u z's Sodium N-phenyl-N- stearoyf-N'-carboxy1ate of the formula GILT-NBC 0 0-, Na+

11 2-B-naphthy1semicarbazide of the formula 2(4-acetamidophenyl)-semicarbazide of the formula 01130 ON'HO-N-NH:

C=O I TH: V 2-(4-bromopheny1)-semicarbazide of the formula I V BrO-NNH2 c' =0 'ILTH2 2-p-t01y1 semicarbazifle of the formula N-acetyl-N-pheny1 hydrazine of the formula CH3 "2-(4-c1iethy1ami1i0pheny1)-semicarbazide of the formulza.

(06m) org-1 14111, 1

V I 2-(4-methoxyphepyl)-semicarbazide of the formula,

DIE-5N "5 I ,N NH: 11 2(1-anthxacy1")eemicarbazide of the formula 1 5 2(2-phenanthry1) semicarbazide of the formula.

+0 NHQ 2(Z-benzo-thiazolyl)-semicarbazlde of the formula.

S C--N--NH2 I V I TH2 Z-IZJE-Carbethoxyfuryl)l-semicarbazide of the formula H(||J-(|JH came 0 c 0% JQ-N-NH:

I 2-[4-(S-carbethoxy-Z-methylthienyl)]-semicarbazide of the '35 formula.

(323L000? 1TT.NH2 CH; dB 20 S 'NH: 40 N-phenyl-N-carbomethoxy hydrazine of the formula 'N-phenyl-N-cyano-hydrazine of the formula 6N =59 2-phenyl-thiosemlcarbazide of the formula.

N-phenyl-N-methyl-Bulfonyl hydrazine of the formula OW Sodium N-phenyl-N-hydrazinesulfonate of the formula @W s0,,M+

N-amino-Npheny1guanidine of the formula v =NH '70 llTH:

As illustrative of the manner in which certain N-acyl-N-arylhydrazines may be prepared may mentioned thereaction of an aryl hydrazine um phthaun anhydride (for the purpose '9! blocking the pi-nitrogen atom); followed by substitution of the remaining u hydrogen atom in the resulting aniline compound by the desired acyl substituent and then splitting off the phthalyl group to obtain the desired final product. For instance, if the product desired is N- benzoyl-N-phenyl hydrazine, phenyl hydrazine is fused with phthalic anhydride at a temperature of 140 to 150 to produce N-anilino-phthalimide according to the following equation:

After the isomeric N-phenylphthalhydrazide which is also formed has been removed, the N- anilino-phthalimide is then acylated with benzoyl chloride by heating in the presence of sodium hydroxide to produce the N-benzoyl derivative ac- 1 cording to the following equation:

- ll N N/ GE NaOlI C 001 The phthalyl group is then split off by treating the acylated phthalimide with hydrazine and then with hydrogen chloride, the reaction taking place as follows:

g reaction will of course be variedzdependin g .upon the particular acylgroupwhichisglesired l in 'the =N-acyl-N-aryl hydrazina or' depending upon the particular aryl group which should be present therein. -If,-for instance, the aryl group is naphthyl, then the original reaction will be carried out with a naphthyl hydrazine instead of phenyl hydrazine. On the other hand, if an -carbamyl' (or substituted carbamyl) aryl hydrazine is desired, such as then the N-anilinophthalimide described above may be treated with isocyanic acid or an ester thereof such as an alkyl, aralkyl, or aryl isocyanate followed by removal of the phthalyl group from the p-nitrogenatom of the hydrazine, thus:

00 N N EN 0 Q. U 0

: CO Q I) =0 oo HNH(R) l?*NHz-HCI In such cases, however, it is not always necessary to employ the phthalyl group for blocking the fi-nitrogen of the aryl hydrazine; aryl hydrazone derived from common aldehydes and ketones have in many cases proved to be useful starting materials. For example, acetone phenyl- N H NH,

and then -40 ,hydrazone may be treated with isocyanic acid or an ester thereof followed by removal of the isopropylidene group as acetone to give a 2- or 2,4-substituted semicarbazide, thus:

CH CH gimme in. cases where arsulfonyl derivatives. are: desired, N -ani1ino phthalimides may be treated with an alkyl or aryl; sulfonyl chloride, followed by removal of the [i-phthalyl group.

N-aryl-N-aminoguanidines. may be prepared by adding cyanamide to anaryl hydrazine, thus:

the N112 In cases where an e-cyano. aryl hydrazine is desired, a cyanogen halide may be used with an aryl hydrazine having a well-blocked.[ii-nitrogen, followed by removal of the unwantedgrounthus;

ONE!

p-Blocked aryl hydrazines may be sulfonated in the a-position by fusion with a metallic bisulfate and by other well-known means.

The effect of the N-acyl-N-aryl hydrazines may be realized in difierent Ways. In one, a soluble azo dye coupling component is added to the N- acyl-N-aryl hydrazine developing solution. In another modification, the; coupling component rendered fast to diffusion. may be incorporatedinv the emulsion. In stillv another modification, both, the; coupling component and the N-acyT-N-aryl' hydrazine renderedv fast to diffusion. may 138.111?- corporated. in. the emulsion. In the latter case, the active NH'z group of the N"-acyli-N'-aryl hydrazine is blocked by converting, it prior to. in corporation in the emulsion, into a group such as --NHOO'O-M+, NHCO OR, NHS 0 -17, or -NH,', nx wherein R, M and X have the valuesprevi'ously' given. These groups prior to coruplingto" form the azo dyes are re'converted to the active N'Hz group: by subjecting the emulsion to an aqueous solution and adjusting the pI-I by the addition of an acid or alkali. For; instance, when: the; amino group iszblocked. by an acid: salt grounan; alkali. is employed, whereas, when a. carbamic' salt. employed, a controlled amount: of. acid; issusedztoi producev the free -NH2- group.

The coupling components; which. are: utilized. for producing the azodyes. by reaction wit-nther- N-acyl-N-aryl hydrazine. under theroxidizingcon ditions prevailing, may be. those. usual in the formation of azo dyes such as; phenols, naphthols, pyrazolones, derivatives. of acetoacetic acid and the like. Compounds falling; within this classification are beta-naphthol, G salt, H acid, K- acid, gamma acid, J. acid, chromotropic acid, naphthionic acid, resorcinol, acetoacetic-o-toluidi'de, R: salt, salicylic. acid, or-cresotini'c acid, 2-: hydroXy-3-naphthoicz acid anilide, 3-methyl -I- phenyl-5ppyrazolone, acetoacetanilide, and the.

like.:

The coupling component andzthe Nt-acyleN-aryl hydrazine may be. rendered. fast: to diffusion by:

612, 2,179,224, 2;I86;045, 2,186,719, 2,186,732, 2,186,- 849 and 2,186,734. The preferred method, however, is to include inthe compoundsa long alkyl chain such as the dodecyl radical, a stearyl radical or the like. As, examples of coupling com- The N.-a-cyl-N-aryl hydrazines referred to above which contain a. stearyl radical are illustrative of such. compounds which. have the property of being fast to difiusion. inv gelatin.v

Certain of; the. N-acyl-N-arylhydrazines may be utilized. not only as the developing agent but as: the coupling agent as well. The compounds. which possess these characteristics are the compounds in the. above formula wherein Ac is --CONIIR and: -CO*0R in which R is a radical.

,of acompound capable of couplingto produce an 'azo dye.

In these compounds, B may, for instance, be. naphthyl or groups derived from. a naphthol, a pyrazolone, anacetoacetic acid ester, etc. Examples, of suchcompounds are Hi-naphthyI-2-phenyl semicarbazide, d-(5-hydroxyelnaphthyl) -2.-phenylsemicarbazide, 4-acetoacetyl- Z-phenylsemicarbazide, *Z-phenyll- (l-phenyl-B- keto-3-pyrazolyl)-semicarbazide and the like...

Apparently these compounds under the'influence of the.- exposedsilverhalideand the alkaline me.- dium. areoxidizedand rearranged to form compounds'which split to give a diazo compound and a. coupling compound. For instance,.in the case. of the 4,-{3-naphthyl-2-phenyl-semicarbazide,, it appears that this compoundrearranges to av diazo ester of the formula CsI-I5N=NOONH Ciel-I7. This ester thereupon splits, giving a diazo compound which is capable of coupling with the naphthylamine portion of the original molecule.

Various methods are available for processing COTOI'" film while, utilizing the N-acy1'-N-aryl hydrazines' of the present invention. One such method involves exposing a photographic element; developing: it to black-andi-white with an ordinary developer such as metol-hydroquinone, washing, reversing by' exposing the residual silver halide to light, and treating the. photographic element with an alkaline developer containing theN-acyl-N-arylhydrazine and an azo coupling component of the type hereinabove' referred to; After bleaching and fixing in the usual manner, there is obtained a positive dye image of the azo dyestuff' resulting from the combination of the hydrazine" compound with. the coupling component.

Another method whichmay be utilized involves incorporating in a. photographic element a coupling component which is fast to difiusi'on in gelatin, for instance, a naphthol containing a long alkyl chain. The emulsion is then exposed and developed in the usual manner. The residual silver halide is subsequently exposed and the emulsion treated with an alkaline developer containing an N-acyl-Nearylhydrazine. After washing, bleaching and fixing, a positive azo dye image is formed in theemulsion.

A further method involves the inclusion in the silver halide emulsion of both the N-acyl-N- arylhydrazine and a nondiifusin'g azo coupling component, ofthe type hereinbefore mentioned.

as above, a negative azo dyestufi' is also produced i in the emulsion.

A further embodiment involves the use of the N-acyl-N-aryl hydrazines which operate both as diazo compounds and as couplers. A gelatinosilver halide emulsion maintained at a pH on the acid side has incorporated therein, for instance, 4 B naphthyl-2-phenyl-semicarbazide sulfate. Upon exposing the emulsion and developing it in an alkaline bath, bleaching and fixing, a negative dyestuif image is obtained in the emulsion. As an alternative of this method, the hydrazine may be located in the developing bath, in which case it may be utilized to develop either a negative latent or a positive latent silver image.

It is to be understood that the invention is not limited to the use of only a single silver halide emulsion. Thus films or plates carrying several emulsion layers may be used as Well as the single layer elements. The layers may or may not all be on the same side of the film base. In addition, the so-called biand tri-pack photographic elements may be used. The invention may likewise be employed for the production of colored prints as well as for the production of transparencies.

The invention is further explained by the accompanying examples, although it is to be borne in mind that the examples are illustrative and not limitative. The parts are by weight unless otherwise stated.

Example I A photographic film carrying a gelatino-silver bromide emulsion is exposed in a camera and developed to black and white in a 3,4-diaminophenol developer. The film is then thoroughly washed, exposed to light, and placed in a colordeveloping solution containing 45 parts of water, 2.5 parts of sodium carbonate, 1 part of R-salt (sodium salt of 2-hydroxynaphthalene-3,6-disulfonic acid), and 15 parts of Z-phenylsemicarbazide [CsH5N(CONH2)NHz]. The temperature is not allowed to go above 20 C. This color development process is allowed to proceed for 20-30 minutes. After this, the film is thoroughly washed and placed in a silver bleaching bath containing potassium ferricyanide, where it is kept until all the silver of the film is converted into silver salts. The silver salts are then removed by treatment with a thiosulfate fixing bath. After washing, the film contains a bright red dye image which presumably has the following structure:

N=NCH5 HS S 0511 Example II [CeHsN (CONHz) NH2] 3 parts and sodium carbonate 5 parts is used. The development is allowed to proceed for 20 minutes during which time the temperature is not allowed to rise above 18 C. When the development is completed, the element is bleached and fixed. Af-

ter washing and drying, the film is found to contain a magenta dyestuff image. This dye has the following probable structure:

011mm ONH N=NC Example III A light-sensitive gelatino-silver halide emulsion is exposed in a camera and developed in a bath consisting of water 90 parts, 3-methyl-1-phenyl- 5-pyrazolone 2 parts, sodium carbonate 5 parts, and 2-phenylsemicarbazide [CsHsN (CONHz) NH2] 3 parts. The developing process is allowed to go on for minutes, care being taken that the ,temperature does not exceed 18 C. After washing, bleaching in a ferricyanide bath, and fixing, the element carries a yellow negative dye image. This dye has the following probable structure:

HOC

Example IV A gelatino-silver halide emulsion is prepared which contains 4% by weight of N-stearoy1-H- salt (disodium 8-stearamido-1-naphthol-3,6-disulfonic acid). This preparation is spread on a suitable base and the resulting light-sensitive element is exposed in a camera and is developed for 25 minutes at 18 C. in a bath [HzN HzNCO) NCsH4CsH4N (CON H2) N H2] and fixed, leaving a clear blue-colored negative dye image.

Example V A light-sensitive silver bromide-gelatin emul- .sion element is exposed and developed in a pmethylaminophenol-hydroquinone type developer. After washing, the element is given a general exposure to light and subjected to a second development in a bath which contains water 93 parts, sodium carbonate 5 parts, and 4- naphthyl-2-phenyl-semicarbazide cam-NH,

2 parts. This second or color development is allowed to proceed for hour, care being taken to keep the temperature below 20 C. After washing, bleaching and fixing as in Example I, the element is found to contain a brownish-yellow positive azo dye image having the following probable structure:

This emulsion is coated onto a suitable support and the light-sensitive element prepared in this way isexposed in a camera. Upon placing this element in a bath consisting of sodium carbonate- 10 parts and water 90- parts, development is ef-' fected'. The element is then thoroughly washed,- bleached, fixed, and washed again, care being taken to prevent the temperature fromrising above 18" C; The element treated in this way contains" a brownish-yellow; negative azo dye image whose chemical structure is probably-the same as that indicated in Example V.

Example VII v A gelatino-silver halide emulsion (having a pH of is prepared containing 3% by weight of- N- benZOyl-N (3-chl0rophenyl) -hydrazine sulfate r and 4% by weight of 2 hydroxy 3-naphthoic acid allilid' This emulsion is spread on asuitable. support and exposed in a camera. The element is then developed by placing it in a sodium car-boa; nate solution. After thoroughly washing, bleaching and fixing and finally washing thoroughly" again, the element is found to contain an orange; negative azo dye image. The probableistructure. of the dye is as follows:

Example VIII A gelatino-silver halide emulsion containing 3% by weight of N-phenyl-N-stearoylhydrazine sulfate. [CcHsN (COC1'IH35) NH2.(H2SO4) g] is coated onto a suitable support and'the lightesensitive element thus produced is exposed in a camera. Development is then effected by placingfithis element in a bath consisting of water 90 parts, sodium carbonate '7 parts and R-salt "3 parts, for minutes at a temperature not ex,- ceeding 18 C. The element is then thoroughly washed, the reduced silver is bleached to a silver salt, and the silver salts present are fixed out with a thiosulfate bath. After washing, there remains a clear red negative azo dye image. This dye has the same probable structure as that indicated for the dye image in Example 1.

Example IX H A gelatino-silver halide emulsion is adjusted to a pH value of 7.8 by addition of sodium acetate,

and-3% by weight of sodium N pheny'l-N-stea royl-N carboxylate ['CsH5N(COC17H35) NHCOONa] is added. This light-sensitive mixture is spread; on a suitable supporting material, exposed in a camera and developed in an alkaline developing bath containing p methylaminophenol hydroq'ui'none. After thoroughly washing, the element is given a general exposure to light. The hy draz'ine developer present in the emulsion is then activated by bathing the element in an. acidic bath. After washing the element, it is developed by bathing it in a bath containing water parts, sodium carbonate 5 parts, and R-salt 5 parts, for 30' minutes at not more than 18 C. After bleach ing, fixing, and washing, the element is found toic'arry a clear red positive azo dye image. .Thedye has the same probable structure as that in-.' dicated for the dye image produced by the method of example I.

' 'Example X The. positive silver image in a photographic film is bleached to a silver ferricyanide image by bathing in a bath containing a ferrocyanide. After: washing, the silver salt image thus formed isconverted into a dye image by bathing the film in a bath consisting of water 90 parts, sodium car-.- bonate. 5 parts, 2-phenylsemicarbazide 3 parts, and sodium p-naphtholate 2 parts. At theend of 30'minutes, the dye image is formed and thereduced silver and residual salts may be recovered by" again bleaching the film in a fer ricyanide and then fixing and washing. The dye; in the dye image, which is a reddish-brown, hasthe following probable structure:

Example XI The positive silver image in a photographic film is converted by bathing the film in a solution containing mercuric chloride. After the film washed, the inorganic salt image is replaced by bathing the, film in a bath containing sodium; p-naphtholate and Z-phenylsemicarbazide as in Example X. The metallic mercury. and silver and their salts areremoved from the film by means of. azcyanide-ferricyanide bleach. There remains in this case,.a reddish-brown dye image similar tothat produced inExample X. e

,I am-cognizant of U. S. P. 2,339,213, which discloses and claims the use of aromatic hydrazines in connection with suitable coupling agents for the productionof dyestuff images in silver halide emulsions. I have found, however, that by comparison, such aromatic hydrazines are inferior to the N-acyl-N arylhydrazines of the present in vention. Aromatic hydrazines of the type' ArNI-INI-Iz (whereAr is: an aryl radical) were usedby Jacobson as early as 1885 as photographic de-' velopers (see German Patent 34,342). However,- because of their. poor. developing properties, these compounds never came into practical use. In this connection it is pertinent to note the state-- ment by Mees in his book entitled The Theory of the Photographic Process (1942) page 339, to the effect that no developing agent of outstanding importance has beenfound among these compounds (meaning by these compoun the arcmatic hydrazines). Such aromatic hydrazines are in many cases harmful to gelatin emulsions, as is evidenced by the necessity of using low temperatures for development and, further, are not sufficiently strong developing agents to develop original latent images as contrasted to bleached images.

The N-acyl-N-aryl hydrazines contemplated herein, however, do not affect gelatin emulsions at ordinary temperatures, i. e., temperatures of around 20 C. In addition, it is not necessary to employ surface-active, dispersing agents or oxidizing agents to assure a satisfactory developing action. They are, moreover, capable of developing original latent images as well as bleached images.

A further important advantage of the N-acyl- N-aryl hydrazines resides in the fact that they are much more stable than the aromatic hydrazines of U. S. P. 2,339,213, and may be prepared and handled with greater ease.

A further advantage in the use of the N-acyl- -aryl hydrazines is found in the double function of certain of these compounds to act both as a developer and as an azo dye coupling component. In other words, the presence of the acyl group on the a-nitrogen atom allows the incorporation of groups capable of fission and recoupling with the hydrazine portion of the molecule to give an azo dye. The N -acyl-N-aryl hydrazines when used as color developers therefore involve a very marked improvement over the aromatic hydrazines of said patent when employed for the same purpose.

The term aryl as used herein and particularly in designating the N -acyl-N -aryl-hydrazines is intended to mean an aromatic radical, i. e., an aromatic hydrocarbon radical or such a radical having substituent groups thereon.

Various modifications of the invention will occur to workers skilled in this art, and I therefore do not intend to be limited in the patent granted except as required by the appended claims.

I claim:

1. The process of producing azo dyestufi images in a photographic element which comprises developing a reducible silver salt image selected from the class consisting of reducible silver halide and silver ferrocyanide with an asymmetrical N -acyl- N-aryl hydrazine in which a terminal group is primary amino while reacting the oxidation products produced from said N-acyl-N-aryl hydrazine by such development with a compound containing a reactive methylene group as an azo dye coupling component to produce an azo dyestuff in situ with the resulting metal image.

2. The process as defined in claim 1 wherein said reducible silver salt image is a silver ferrocyanide image.

3. The process of producing azo dyestufl images in a photographic emulsion containing a reducible silver salt image selected from the class consisting of reducible silver halide and silver ferrocyanide images, and also containing a compound containing a reactive methylene group, fast to diffusion, as a coupling component which comprises developing said developable image with an asymmetrical N -acyl-N-aryl hydrazine in which a terminal group is primary amino while reacting the oxidation products produced from said N- acyl-N-aryl hydrazine by such development with said coupling component to produce an azo dye in situ with the resulting metal image.

. 4. The process as defined in claim 3 wherein said reducible silver salt image is a latent silver halide image. 1

5. The process as defined in claim 1 wherein said compound containing a reactive methylene group is a pyrazolone.

6. The process as defined in claim 1 wherein the compound containing a reactive methylene group is an acetoacet compound.

7. The process of producing positive azo dyestuif images in a photographic silver halide emulsion which comprises exposing the emulsion, developing the same in a black and white developer, re-exposing the residual silver halide and developing the residual silver halide with an asym* metrical N-acyl-N-aryl hydrazine in which a ter-- minal group is primary amino while reacting the oxidation products produced from said N -acyl-N- aryl hydrazine by such development with a compound containing a reactive methylene group as a coupling component to produce an azo dye in situ with the resulting silver image.

8. The process as defined in claim 7 wherein the compounds containing a reactive methylene group is a pyrazolone.

9. The process as defined in claim 7 wherein the compound containing the reactive methylene group is an acetoacet compound.

10. A photographic silver halide emulsion containing a compound containing a reactive methylene group fast to diffusion as a coupling component and as a developer an asymmetrical N- acyl-N-aryl hydrazine having a terminal group selected from the class consisting of primary amino and amino substituted by an acid group which splits off with regeneration of a primary. amino group upon change in pH and the salts of said hydrazine.

11. A photographic developer comprising an alkaline solution of a compound containing a reactive methylene group as a coupling component, and an asymmetrical N -acy1-N -aryl hydrazine in which the terminal group is primary amino, said hydrazine acting as the active developing ingre-' client.

12. The process of producing dyestuif images in a silver halide emulsion which comprises ex-- posing the emulsion and color developing the same with a solution containing 1-phenyl-3- methyl-5-pyrazolone and Z-phenyl semicarbazide.

13. A photographic color developer comprising an aqueous alkaline solution of l-phenyl-B-methyl-5-pyrazolone and 2-phenyl semicarbazide.

WILLIAM E. HANFORD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Handbook of Photography, Henney and Dudley, 1939, Whittlesey House, page 332 cited; (Copy in Division 7.)

Friedman, American Photography, June 1937,- p. 448 cited. (Copy in S. L.)

Mees, The Theory of the Photographic Process, The MacMillan 00., N. Y., 1942, page 356 cited. (Copy in Div. 67.)

fiertificate of Correction Patent No. 2,495,000 January 17, 1950 WILLIAM E. HANFORD It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 14, line 24, for ferricyanide read ferrocyanide; line 25, for ferrocyanide read ferricyanide; column 15, line 48, after ferrocyanide insert images;

and that the said Letters Patent should be read with these corrections therein that I the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 9th day of May, A. D. 1950.

THOMAS F. MURPHY,

Assistant Uommz'caz'oner of Patents. 

1. THE PROCESS OF PRODUCING AZO DYESTUFF IMAGES IN A PHOTOGRAPHIC ELEMENT WHICH COMPRISES DEVELOPING A REDUCIBLE SILVER SALT IMAGE SELECTED FROM THE CLASS CONSISTING OF REDUCIBLE SILVER HALIDE AND SILVER FERROCYANIDE WITH AN ASYMMETRICAL N-ACYLN-ARYL HYDRAZINE IN WHICH A TERMINAL GROUP IS PRIMARY AMINO WHILE REACTING THE OXIDATION PRODUCTS PRODUCED FROM SAID N-ACYL-N-ARYL HYDRAZINE BY SUCH DEVELOPMENT WITH A COMPOUND CONTAINING A REACTIVE METHYLENE GROUP AS AN AZO DYE COUPLING COMPONENT TO PRODUCE AN AZO DYESTUFF IN SITU WITH THE RESULTING METAL IMAGE. 